Communications between satellite, sea, air, and ground communication devices have made our world seem smaller and smaller. Increasingly so, moreover, worldwide communications are in an internet protocol such as TCP/IP, UDP, IPV-6 and those protocols that are backwards compatible. There are, however, older, reliable, and very expensive communication devices, called legacy devices that do not transmit and/or receive data in an internet protocol. Examples of such legacy devices include radio communications, satellite communications (SATCOM), and telecommunications that include Wide Bandwidth Satellite Communications (WB SATCOM), Narrow Bandwidth Satellite communications (NB SATCOM), Common Data Link, (CDL), Very High Frequency (VHF)/Ultra High Frequency (UHF) Line of Sight (LOS) Radio Communications. Communication devices, e.g., airplanes, ocean-going vessels, Hum-Vees, motorcycles, etc., moreover, are mobile and some, like satellites, are constantly in motion. Data communicated between these devices also have different information sensitivity levels from top secret national security or military information to public general weather information in different languages.
To illustrate the complexity of these communications, an analysis of one type of communication system is presented as the background herein—manned aircraft to ground control. This will familiarize the reader with the different hardware involved in world-wide communications, the software or data processing of these communications that occurs both on the ground and in the air, different industry specifications and standards involved, different protocols, the different signals, etc. Keep in mind that this example is only between a manned aircraft and a ground station; there are also communications between aircraft and aircraft, watercraft, both from the surface of the water and submarines, satellites, ground control stations, ground mobile stations, unmanned aerial and ground vehicles, manned ground vehicles, space stations, etc.
Currently, there are three networks through which an aircraft can communicate with ground control: VHF, SATCOM, and HF. A network of VHF radio ground stations ensure that aircraft can communicate with ground stations in real-time. VHF communication is line-of-sight and the typical VHF range is dependent on altitude with a 200-mile transmission range common at high altitudes; thus, VHF communication is applicable only over landmasses which have a VHF ground network installed. SATCOM, on the other hand, provides worldwide coverage except at the high latitudes such as over the poles. SATCOM refers to satellite communications and airborne SATCOM equipment includes a satellite data unit, a high power amplifier, and an antenna with a steerable beam. High Frequency (HF) datalink is a relatively new network responsible for maintaining communication of aircraft on polar routes with ground based systems.
Aircraft Communication Addressing and Reporting System (ACARS) refers to a complete air and ground digital datalink system for transmission of small messages between aircraft and ground stations via radio or satellite using telex formats. As air traffic increases, however, ACARS will no longer have the capacity or flexibility to handle the large amount of datalink communications so an Aeronautical Telecommunications Network (ATN) protocol will replace ACARS and provide services such as authentication, security, and a true internet protocol working architecture. In many cases, the voice-relayed information involves dedicated radio operators and digital messages sent through an ATN to an airline teletype system or its successor system.
There are three major parts of the ACARS datalink system: (a) aircraft equipment; (b) a service provider; and (c) a ground processing system. The heart of the datalink system on board the aircraft is the ACARS Management Unit, referred to herein as the avionics computer; newer versions are referred to as a communications management unit and defined in ARINC Characteristic 758. The avionics computer is designed to send and receive digital messages from the ground using existing VHF radios. Messages that are sent to the ground from the avionic computer are referred to as downlink messages; messages transmitted to an aircraft or other system are called uplink messages. Aircraft equipment also consists of airborne end systems that are the source of ACARS downlinks and the destination for uplinks, such as the Flight Management System (FMS), a datalink printer, a maintenance computer, and the cabin terminal. The avionics computer is also a router that routes a downlink message through the most efficient air-ground subnetwork. Of course, a communications avionics computer may also be an end system for certain messages. The aircraft may also have a multifunction control display unit that is a text-only device that displays messages to the aircrew and accepts crew input on an integrated keyboard. Standards for the display unit are defined in ARINC Characteristic 739 to have seven input ports and can be used with seven different systems, such as avionics computer or flight management system.
The ground end system is the destination for downlinks, and the source of uplinks. On the ground, the ACARS system is a network of radio transceivers that receive and transmit messages, as well as route the messages to various airlines on the network. Of course, there were and are many standards promulgated by the telecommunications and airline industry with which the equipment and the communication must comply, such as the ARINC 758 for avionics computers. Generally, ground end systems are military and government agencies such as CAA/FAA, or airline operations headquarters to provide air traffic services such as clearances, etc. Airline operations provide the information necessary for operating the airline efficiently, such as gate assignments, maintenance, passenger needs, etc. In the beginning most airlines created their own legacy host systems for managing their ACARS messages but now several off-the-shelf products manage the ground hosting and enable an end user to receive downlinks, send uplinks, reformat messages, distribute messages, track communications and much more. There is also a capability for collating, parsing and reformatting ACARS messages for delivery into airline systems and then provide a return path via the ACARS networks to the originating or other aircraft in the fleet; this capability has been extended into the eFlight concept for integrated airlines operations.
Typical datalink functions include: (1) flight management that sends flight plan change requests, position reports, receives clearances, controller instructions, etc.; (2) printers that may automatically print an uplink message; (3) and maintenance computer(s) that may downlink diagnostic messages. In advanced systems, in-flight troubleshooting can be conducted by technicians on the ground using datalink messages to command diagnostic routines in the maintenance computer and analyzing the downlinked results. There is also a (4) cabin terminal to communicate special needs of passengers, gate changes due to delays, catering, etc. In addition, the router function built into the avionics computer determines which subnetwork to use, i.e., HF, VHF, or SATCOM, when routing a message from the aircraft.
ACARS messages may be of three types: (a) Air Traffic Control (ATC) messages, defined in ARINC Standard 623, used by aircraft crew to request clearances, and by ground controllers to provide those clearances; (b) Aeronautical Operational Control (AOC) and (c) Airline Administrative Control (AAC), to communicate between the aircraft and its base, whose avionics computers and hardware may be proprietarily defined by the users but must meet at least the guidelines of ARINC Standard 618, or may be standardized according ARINC Standard 633. ACARS is programmed to automatically detect and report changes occurring during the major flight phases, i.e., Out of the gate, Off the ground, On the ground and Into the Gate (OOOI), by monitoring sensors on the aircraft. In addition to detecting OOOI events on the aircraft and sending messages automatically to the ground, the systems were expanded to support new interfaces with other on-board avionics to include a datalink interface between the ACARS avionics computers and flight management systems for transmission and receipt of flight plans and weather information. Now flight management systems are updated in flight, and new weather conditions or alternate flight plans are evaluated in real time.
Other messages include fuel consumption, engine performance data, and aircraft position as well as free text data. Typically, a SATCOM installation supports a datalink channel as well as several voice channels. Messages are sent to the ground from other on-board systems. As an example, algorithms of a flight data acquisition and management system (FDAMS) analyze engine, aircraft, and operational performance conditions and provide real-time data to a maintenance crew on the ground, examples of which include monitoring engine exceedance conditions during flight such as checking engine vibration or oil temperature exceeding normal operating conditions. Abnormal flight conditions and detailed engine reports for engine trending enable airlines to better monitor engine performance and identify and plan repair and maintenance activities while the aircraft was still in flight. Furthermore, a control display unit located in the cockpit allows the flight crew to send and receive messages similar to today's email, e.g., requesting weather information and ambulance services for passenger becoming ill. Some responses are automatic, such as ground computers transmitting the requested weather information back to the ACARS avionics computer, which could then be displayed and/or printed; of course, others such as medical emergencies may be communicated over SATCOM voice protocols. Airlines have added new messages to support new applications, such as weather, winds, clearances, connecting flights, etc. so that the ACARS systems have been customized to support airline unique applications, and unique ground computer requirements, resulting in each airline having their own unique ACARS application operating on their aircraft. Some airlines have more than 75 display units or monitors for their flight crews, where other airlines may have only a dozen different screens. In addition, because each airline's ground computers may be different, the contents and formats of the messages sent by an ACARS avionics computer are different for each airline. Military aircraft, moreover, may have much higher security and stricter data requirements than commercial airlines.
The ACARS avionics computer sends a message to one of the existing HF, SATCOM or VHF radios as selected by logic within the avionics computer. For a message over the VHF network, an on-board radio would transmit the VHF signals to be received by a VHF ground station. The majority of ACARS messages are typically only 100 to 200 characters in length and such messages are made up of a one-block transmission from (or to) the aircraft. One ACARS block is constrained to 220 characters within the body of the message. For downlink messages which are longer than 220 characters, the ACARS unit will split the message into multiple blocks, currently no more than 16, and transmit each block to the ground station. For these multi-block messages, the ground station collects each block until the complete message is received before processing and routing the message. The ACARS avionics computer also contains protocols to support retry of failed messages or retransmission of messages when changing service providers.
Once the ground station receives the complete message from an aircraft, the ground station forwards the message to the datalink service provider. The datalink service provider delivers the message from the aircraft to the ground end system, and vice versa. Because the ACARS network is modeled after the point-to-point telex network, all messages go to a central processing location or the datalink service provider's main computer system. The datalink service provider routes the message to the appropriate end system using its network of landlines and ground stations. The datalink service provider uses information contained in a routing table to process the message by identifying each aircraft and the type of messages and then forwards the message to the airlines or other destinations.
There are currently two primary datalink service providers of ground networks in the world, ARINC and SITA, although specific countries have implemented their own network with the help of either ARINC or SITA. Until recently, each area of the world was supported by a single service provider but now both ARINC and SITA are competing and installing networks in the same regions. ARINC operates a network in North America, and have also recently started operating a network in Europe. ARINC has also assisted the CAAC in China, as well as Thailand and South America with the installation of VHF networks. SITA has operated the network in Europe, Middle East, South America and Asia for many years and have also started a network in the US to compete with ARINC.
Each airline must tell its service provider(s) what messages and message labels their ACARS systems will send, and for each message, where to route the message. The service provider then updates their routing tables. Correlating a label within the message header with the routing table, the datalink service provider forwards the message to the airline's computer system. The transmission time from when the flight crew presses the send key to send the message, to the time that it is processed within an airline's computer system varies, but is generally on the order of six to fifteen seconds.
For a message to be transmitted from the ground to the aircraft, i.e., an uplink message, the process is nearly a mirror image of how a downlink is sent from the aircraft. For example, in response to an ACARS downlink message requesting weather information, a weather report may be automatically constructed and sent by the airline's computer system. The message contains the aircraft registration number in the header of the message with the body of the message containing the actual weather information. This message is sent to the datalink service provider's main computer system. The datalink service provider transmits the message over their ground network to a VHF ground station in the vicinity of the aircraft. The ground station broadcasts the message over the VHF frequency. The on-board VHF radio receives the VHF signal and passes the message to the communications avionics computer having an internal modem that transforms the signal into a digital message. The avionics computer validates the aircraft registration number, and processes the message. The processing performed on the uplink message by the avionics computer depends on the specific airline requirements. In general, an uplink is either forwarded to another avionics computer, such as in-flight management system or FDAMS, or is processed by the on-board avionics computer.
Presently, each communication system is an independent network with redundant hardware, if necessary, including multiple different interfaces with different data. SATCOM communication has its own hardware and software; VHF communication has its own hardware and channels. Often, the VHF and UHF radios are not connected to other communication interfaces. What is needed then is a single integrated architecture that allows world-wide and local communications to be converted in and out of internet protocol. Also, with the increased communications, it is imperative that any inherent and recognizable security level of the information be preserved.
Further, what is required is a dynamic and automated method and service that converts non-internet protocol data and routes this data over a network having both secure and nonsecure lines and devices. These needs and other that will become apparent are solved by the invention as stated below: